This is a two-year case-control study of 225 cases and matched controls resident in Northern New Jersey. All white males between the ages of 30 and 64 years in the selected counties with a diagnosis of malignant melanoma who were first diagnosed between July 1, 1978, and December 30, 1980, will be eligible as cases. Age-sex-race population matched controls will be selected. Information obtained from records of private dermatopathology laboratories and hospital pathologist records will be used to determine cases aided by the New Jersey, New York and Pennsylvania cancer registers. All cases will be ascertained as malignant melanoma by a board certified dermatopathologist. Home interviewing of cases and controls will obtain information on: residence history, work exposure history (particularly to chemical substances), sun exposure, history of cancer in the family and history of chloracne dermatitis. Preliminary work has provided suggestive evidence of a large relative risk of malignant melanoma among workers exposed to polychlorinated biphenyls (PCBs) and other chemicals. New Jersey has been selected as the locale for the study because this state has the largest number of workers in chemical and related industries in the nation and because high melanoma mortality rates (for an area outside the South) have been noted among males. Investigation will be carried out to determine if there are significant differences between cases and controls in exposure to chemical substances, exposure to sunlight, or a previous history of chloracne dermatitis.